Hydraulic circuits used for outrigger cylinders in the related art include, for instance, the hydraulic circuit disclosed in Japanese Laid Open utility Model Publication No. S63-4772.
In the hydraulic circuit disclosed in this publication, the bottom chambers or the rod chambers of outrigger cylinders disposed to the front, the rear, the left and the right sides of the vehicle are made to communicate individually via a hydraulic pilot switching valve. In response to a switching operation at the switching valve, pressure oil is allowed to flow to a desired hydraulic cylinder while cutting off the flow of pressure oil to the other hydraulic cylinders. This system makes it possible to operate the outriggers on the front side, the rear side, the left side and the right side independently of one another.
The operation that needs to be performed to select a specific outrigger in the circuit having outriggers that can be operated independently of one another tends to be complicated.